ABSTRACT Persistent unresolved inflammation impairs diabetic wound healing. The function and fate of wound monocyte/macrophages hold the key to the outcome of wound inflammation. This proposal builds on observations originating from live functional wound macrophages (wm?) and wound fluid (WF) derived from chronic wounds of patients which were then developed further using experimental models. Given current ambiguity in macrophage nomenclature, and proposed misfit of wm? with the M1/M2 nomenclature, for this proposal we classify ?m? based on the pro-inflammatory (m?inf) or pro-resolution/healing (m?heal) functional states. During the last cycle, we reported that i) successful wm? efferocytosis (Eff) helps resolve inflammation; and ii) that efferocytosis was severely impaired (Efflo) in wm? of diabetic wounds causing unresolved inflammation. Recently, our laboratory was the first to report a critical role of miRNA-21 in the regulation of wound inflammation. The proposed study recognizes (i) ?m? efferocytosis functional status, and (ii) ?m? miR- 21 as two critical factors required for advancing pro-inflammatory wm? (m?inf) to m?heal. wm? are attractive therapeutic target for improved wound healing outcomes. Importantly, through nanoparticle based m? targeted delivery of miR-21, and rMFG-E8 application, both factors may be modified with therapeutic intent. Another seminal observation is the detection of FSP1+Collagen1A1 producing fibroblast-like cells (m?F) of myeloid origin at wound-site. This raises the question, do plastic wm? transition to fibroblast-like cells at the wound site? We hypothesize that in the wound microenvironment, efferocytosis and miR-21 are critical determinants of wm? reprograming of m?inf?m?heal or m?inf?m?F functional states. Diabetic wm? suffer from Efflo and miR- 21lo. This combination stalls wm? in m?inf resulting in chronic inflammation. The following 3 aims are thus proposed: Aim 1: Test efferocytosis and miR-21 as critical determinants of wound monocyte/macrophage (wm?) fate. 1.1 A subset of wm? undergoes m?inf?m?heal; 1.2 Another unique subset of wm? undergoes m?inf?m?F. Aim 2: Determine how diabetes redirects the fate of wm? resulting in derailment of healing. 2.1 Diabetic wm? suffer from two critical impairments, impaired efferocytosis (Efflo) and low miR-21 (miR-21lo), the combination of which stalls wm? in m?inf; 2.2 Targeted nanoparticle delivery of miR-21 to diabetic wm? advances some such cells primarily to m?F; 2.3 In diabetic wm?, correction of miR-21 (2.2) in combination with correction of efferocytosis resumes physiological healing advancing diabetic m?inf?m?heal/m?F. Aim 3: Study live wm? and wound-edge tissue biopsies isolated from wounds of diabetic patients testing whether 3.1 wm? transition to m?F; 3.2 correction of miR-21 and efferocytosis advances diabetic wm? to m?inf?m?heal/m?F .